Heat gun defroster



Sept. 28, 1965 J. s. GRAVES HEAT GUN DEFROSTER Filed June 27, 1965 IN VEN TOR.

United States Patent 3,209,127 HEAT GUN DEFRO'STER Joel S. Graves, Flint, Mich., assignor to The Ameriplastic Company, Inc., Flint, Mich, a corporation of Michigan Filed June 27, '1963, Ser. No. 291,014 1 Claim. (CL 219-370) The present invention relates to defrosters and more particularly to portable, electric, forced hot air defrosters for defrosting the Windshields of motor vehicles.

An object of the invention is to provide an improved portable electric hot air defroster.

Another object of the invention is to provide improved means for heating a current of air within a forced hot air defroster.

Broadly, the present invention includes a gun-shaped case of plastic or similar material having an air intake port and an air outlet port therein, a small rotary fan arranged to force outwardly through said air outlet port air drawn inwardly through said intake port, a small electric motor arranged to rotate said fan, an electric resistance element arranged to heat said outwardly directed air, a plug adapted for connection with the electrical system of a motor vehicle by insertion in the cigar lighter socket, and electric wiring operatively interconnecting said plug with said motor and heater element to energize same. An insulated heat chamber is provided surrounding said resistance element and through which the fiow of outwardly directed air is constrained to pass. The unique configuration of the heat chamber is such as to impart to the outwardly directed air an unusually high temperature while increasing the efi'iciency of the device, reducing the amount of current required, eliminating the overloading of the vehicles electric circuit, and lengthening the life of the resistance element.

The above and other objects of the invention which will later become apparent as the following description proceeds, are attained by the present invention, a preferred embodiment of which has been illustrated, by way of example only, in the accompanying drawing, forming a part of this specification in which like characters are employed to designate like parts throughout the same, and wherein:

FIGURE 1 is a side sectional view of a heat gun defroster.

FIGURE 2 is a view taken along line 22 of FIG- URE 1.

FIGURE 3 is a side view of a portion of the handle of the heat gun defroster of the invention.

FIGURE 4 is a view of a heat gun defroster in operation.

Referring now more particularly to the drawings, I provide a gun-shaped case preferably formed of two symmetrical sections of plastic or other inexpensive, durable, light-weight material, mutually engaged by screws 11 or the like inserted transversely through one section and threadably engaged within threaded sockets 12 extending from the inner surface of the other section. A generally circular air inlet port 13 is formed in the top of case 10 near the rear thereof, and an air outlet port 14 is formed at the forward or muzzle end of the case. A squirrel cage type rotary fan 17 is operatively mounted upon the shaft of a small electric motor 18 within the receiver portion of case 10, and the motor, in turn, is mounted within the handle portion of the case by any convenient mounting means such as a screw extending through the sidewall of the handle portion of the case and threadably engaged within a threaded aperture 20 in the outer wall of the motor. Fan 17 is thus supported below air inlet port 13. A flange 24 surrounding the upper end of a sleeve 22 is supported within a circular channel 26 surrounding the inside of air inlet port 13, so that the lower end of the sleeve extends downwardly to a point slightly above fan 17.

I provide an insulated heat chamber generally indicated at 28 formed of ceramic material 29 and mounted within the barrel portion of case 10 by a bolt 30 or the like extending transversely through the case and said heat chamber. A large bore 32 extends longitudinally through heat chamber 28 and bears at one end a smoothly flared mouth 34 which opens upon and in close proximity to fan 17, and bears at the other end a wall 35 in which is formed a rectangular orifice 36 of relatively smaller crosssectional area and which opens upon air outlet port 14.

A heating element 38, consisting of an electrical resistance wire, is disposed within bore 32, the conventional spring-like structure of such element causing it to be frictionally retained within the bore solely by contact with the ceramic wall of the bore without the use of a ceramic core or other supporting means which would interfere with the flow of air through the bore and around the heating element.

An electrical plug 40 adapted to be operatively received within the conventional cigar lighter socket of a motor vehicle 42 transmits electrical energy from the electrical system of the vehicle to energize motor 18 and heater element 38 through electrical wires 44.

In operation, when plug 40 is inserted into the cigar lighter socket of motor vehicle 42, electrical current is transmitted through wires 44 and energizes both electrical motor 18 and heater element 38, causing fan 17 to rotate and the heater element to radiate heat within bore 32 of heat chamber 28. The motion of fan 17 forces air forwardly and outwardly from case 10 through mouth 34, bore 32, orifice 36, and air outlet port 14. As such air passes through bore 32, it is heated by contact with heater element 38 and by heat energy radiated from said element.

The handle portion of the device is gripped manually by the operator and the barrel portion aimed in a natural manner toward the windshield or other pane of glass from which frost or ice is sought to be removed. The length of the cord is sufficient so that not only the inner surface of such pane of glass may be thus defrosted but also the operator may pass the device through an open window or door of the vehicle and employ the device outside of the car, as illustrated in FIGURE 4, while plug 40 is still engaged within the cigar lighter socket of the vehicle.

The insulative properties of the ceramic material composing the body of heat chamber 28 substantially prevents heat loss radially from the barrel portion of case 10, and such heat as is radiated rearwardly through mouth 34 usefully serves to preheat that air within the rear portion of case 10 which is almost immediately forced forwardly through mouth 34 and bore 32 by fan 17 anyway. The air thus heated and forced outwardly through air outlet port 14 is replaced by atmospheric air drawn downwardly into case 10 through air intake port 13 normal to the plane of movement of fan 17.

Particular attention is invited to the configuration of heat chamber 28 and to the unique functions performed thereby. When air is being forced steadily through heat chamber 28, the equal masses of air will necessarily pass through orifice 36 during a fixed interval of time as will pass a section taken at any point within bore 32 during the same fixed interval of time. Thus the forward velocity of the air passing through orifice 36 is necessarily greater than the forward velocity of air passing through bore 32, to enable such equal masses of air to pass through the orifice and a section within the bore during such fixed interval of time. The slower forward velocity of such air within bore 32 increases the length of time that the air is in the proximity of heater element 38 and heated thereby, with the result that when such air passes outwardly through the air outlet port 14 it has a considerably higher temperature than would be the case if the flow were not restricted forwardly of heater element 38 by orifice 36.

Srnoothly flared mouth 34 is adapted to minimize turbulence in the air entering bore 32 upstream of heating element 38. Wall 35, however, arranged transversely to the longitudinal axis of bore 32 and extending across a substantial portion of the cross-section of the bore surrounding orifice 36, as best shown in FIGURE 2, is adapted specifically to create turbulence in the heated air within the bore downstream of heating element 38. This turbulence promotes the mixing within the bore of portions of such heated air of greater and lesser temperature, so that the air emerging through orifice 36 is of uniform temperature. The area of a windshield or other surface upon which the flow of air is directed by the device is thus heated uniformly. The rectangular shape of orifice 36 permits the device to be used to heat efficiently in the nearly right-angled corner areas of a windshield.

I have found that where no heat chamber 28 with this unique configuration is provided, fifteen to eighteen amperes of electrical current is required to produce at air exhaust port 14 air having a temperature of from'l50 degrees Fahrenheit to 175 degrees Fahrenheit, and such flow of current frequently causes the fuses of the electrical system of the motor vehicle to be blown. When heat chamber 28 is employed, however, I have found that only approximately eight and one-half amperes of electrical current is required to produce at air exhaust port 14 air having a temperature of approximately 200 degrees Fahrenheit. Heat chamber 28 thus increases the air temperature at outlet port 14 by 12.5% to 25%, but, even more importantly, does so with a current drain of only' 47% to 57% of that required where the heat chamber is not used. Thus not only the effectiveness of the device as a defroster is increased but the efficiency thereof is dramatically increased with less drain on the source of electrical energy, increased life for heater element 38, and.

What is claimed is:

In combination, a gun-shaped case of molded plastic, said case having a handle portion and a barrel portion; said handle portion having an air inlet port; said barrel portion having a muzzle end and an air outlet port at said muzzle end; an annular ceramic heat chamber mounted Within said barrel portion, said heat chamber having a longitudinal bore extending therethrough, a coaxial outwardly flared mouth at the end of said chamber adjacent said handle, a transverse wall at the end of said chamber adjacent said muzzle end of said barrel potion, said wall extending across a substantial portion of the cross-section of said bore, and a coaxial orifice in said wall of small cross-sectional area relative to the crosssectional area of said bore and opening upon said outlet port, said ceramic chamber being thicker than said barrel portion of said case adjacent thereto, whereby said ceramic chamber provides thermal insulation for said barrel portion of said case; an open spiral coil electric resistance heating element f'rictionally retained within said bore by the inherent resilience of said spiral coil; an electric motor mounted within said handle portion of said case; a fan operatively mounted upon said motor and arranged to force air forwardly into and through said mouth, said bore, and said orifice and outwardly through said outlet port of said case; an electric plug adapted to be operatively received within the cigar lighter socket of a motor vehicle, and means for transmitting electric current from said plug to said motor and said heating element to electrically energize same.

References Cited by the Examiner UNITED STATES PATENTS 1,465,292 8/23 Wessig 219364 1,564,896 12/25 Rinker et a1 219370 1,738,164 12/29 Zingg 2l9374 X 1,777,744 10/ 30 Breuer 219373 1,821,525 9/31 Nielsen 219370 1,977,151 10/34 Schottky 219261 2,121,753 6/38 Cornell.

2,432,067 12/47 Morse 219-374 X 2,514,528 7/50 Wahl 219--368 2,551,777 5/51 Werner 219364 3,026,401 3/62 Cheviron 219-3 69 X FOREIGN PATENTS 1,254,781 v 1/ 61 France.

ANTHONY BARTIS, Acting Primary Examiner. 

